1. Field of the Invention
The present invention relates to a battery. More particularly, the present invention relates to a battery suitable for use as a rechargeable battery, the battery including a lead element for collecting current generated by an electrode assembly.
2. Description of the Related Art
Generally, batteries include single use, or non-rechargeable, and secondary, or rechargeable, batteries. Typical rechargeable batteries may be discharged and recharged multiple times, whereas single-use batteries are typically disposed of after an initial discharge.
Batteries may be fabricated in a variety of sizes. Small batteries may be formed of a unit battery cell, or of a plurality of unit battery cells configured as a battery pack, and may be used as power sources for various portable electronic devices, e.g., cellular phones, laptop computers, camcorders, etc. Larger batteries may be formed of multiple interconnected batteries, e.g., packs of several to tens of unit battery cells connected together, and may be used to power motors and motor-driven machines such as electric vehicles (EVs), hybrid electric vehicles (HEVs), etc.
Rechargeable batteries may be classified according to their form factor, e.g., cylindrical, prismatic or rectangular, etc. Rechargeable batteries may include an electrode assembly that is formed by winding positive and negative electrode sheets with an interposed separator that serves as an insulator. In other cases, the battery may include multi-layered stacked positive and negative electrodes with an insulating separator in between. The electrode assembly may be inserted into a case that is closed with a cap assembly having external terminals protruding therefrom, for electrical connection to the apparatus to be powered.
Where the positive and negative electrodes and the separator are spirally wound in an electrode assembly, leads may be attached to the electrode assembly to collect current generated by the positive and negative electrodes. The leads may be connected to the external terminals in order to deliver electrical current generated by the positive and negative electrodes to the outside of the case.
Rechargeable batteries with high energy density that employ a non-aqueous electrolyte have recently been developed as high power rechargeable batteries. Very large-capacity batteries, e.g., those used for EVs and HEVs, may have bigger positive and negative electrodes in order to accommodate large current flows. In order to reduce the internal resistance of the battery, these batteries may have leads with an additional tab to maximize a current collecting area at the interface between the electrodes and the leads. However, such leads may be difficult to weld to the electrodes, and it may be difficult to keep the tab properly aligned with respect to the electrodes during manufacturing.
For example, the battery may be assembled by welding the tab to an uncoated or exposed region of the respective electrode, i.e., to a portion of the respective positive or negative electrode that extends from the electrode assembly. The welding process may involve the application of pressure to the electrode assembly, and such pressure may disturb the alignment of the tab before it is fixed in place by the welding. Even when the tab is correctly inserted in the first instance, it may be displaced due to the pressure applied for welding, causing an alignment problem between the tab and the exposed region of the respective electrode. Weld and alignment problems such as these may result in difficulty assembling the batteries, defective batteries, reduced performance characteristics of the finished batteries, etc.
One way to address the problems that arise during welding is to fix the tab in place by attaching tape between the tab and the exposed region of the electrode, i.e., after the tab is inserted into the exposed region and before welding. However, such an approach adds time and effort to the manufacturing process, thus decreasing productivity.